1. Field of the Invention
The invention relates to the handling of traffic flows in a mobile communications network, and in particular in a network which has access to an external packet data network such as the internet or any other packet-based system.
2. Description of the Related Art
Mobile communications systems refers generally to any telecommunications systems which enable a wireless communication when users are moving within the service area of the system. A typical mobile communications systems is a Public Land Mobile Network (PLMN).
Often the mobile communications network is an access network providing a user with a wireless access to external networks, hosts, or services offered by specific service providers. The user must have a subscribership with the mobile communications system in order to be able to use the services of the mobile system. Normally, in addition to the mobile subscribership, a separate subscribership is needed with each one of the other service providers whose services are accessed through the mobile communications network. The mobile subscriber data of the user may indicate which external service the user is authorized to use and to which access point or gateway node a service request should be routed. The access point or gateway node then provides further access to an external network or an external host. In this case the service request is routed on the basis of a service definition in the mobile subscriber data stored by a mobile network operator, and therefore there is no need for further authentication of the user by the gateway or the service provider.
It is, however, desirable that the user is able to select the service provider or the most suitable access point of the service provider. For example, the use of the TCP/IP (Transmission Control Protocol/Internet Protocol) data network, i.e. the Internet network has increased very rapidly. Before the user can connect to the Internet, he has to have a contract with an Internet service provider ISP, who provides access to the Internet via one or more Internet access points IAP.
The general packet radio service (GPRS) is a new service in the GSM system, and is one of the objects of the standardization work of the GSM phase 2+ at ETSI (European Telecommunication Standard Institute). The GPRS operation environment includes a number of packet data service nodes (SN), which in this application will be referred to as serving GPRS support nodes (SGSN), each of which is connected to the base station subsystem by way of base station controllers (BSC) in such a way that it can provide a packet service for mobile data terminals via several base stations, i.e. cells. The SGSN are in turn connected to an external data network, e.g. to a public switched data network (PSPDN), via GPRS gateway support nodes (GGSN). The GPRS services thus allow to provide packet data transmission between mobile data terminals and external data networks when the GPRS network functions as an access network.
In GPRS network the mobile station MS may optionally indicate, in a message requesting to activate a packet data protocol (PDP) context in the network, an access point name for selection of a reference point to a certain external network. A SGSN authenticates the mobile user and sends a PDP context creation request to a gateway node GGSN selected according to information stored in the subscriber data or according to the access point name given by the MS, or to default GGSN known by the SGSN.
In such a network, a PDP context is established to carry traffic flows over the network, each PDP context including a radio bearer provided between the mobile data terminal or user equipment and the radio network controller, a radio access bearer provided between the user equipment, the radio network controller and the SGSN, and switched packet data channel provided between the serving GPRS service node and the gateway GPRS service node. Each PDP context can carry more than one traffic flow, but all traffic flows within one particular PDP context are treated the same way as regards their transmission across the network. The PDP context treatment requirement is based on PDP context attributes, for example quality-of-service and/or charging attributes.
A PDP context is requested by the user equipment, and the GGSN requests quality-of-service (QoS) authorization from a policy decision function (PDF) in the network. Once authorization has been obtained, the GGSN proceeds with the PDP context activation. However, it can happen that the quality-of-service parameters are modified e.g. during set up of the radio bearer and radio access bearers due to the network environment, even after authorization for a particular treatment has been obtained. Another problem can arise in a situation where user equipment (UE) can request a bearer service with a QoS profile. The UE does not know specifically what QoS will be supported by the network. In the case that the network rejects the service with the requested bitrate, UE has to request the service again with a lower bitrate. This causes much signaling flow between the terminal and the network if the network rejects the requested QoS which is made by the UE all the time.